obtaining the JSP Tag Attributes from a bean

I am retrieving values from a bean and trying to set those to the attributes of a custom tag. <mytag:textfield myFieldValue="abcd" /> Here instead of the string "abcd" ... I would like to populate it from a value obtained by querying a bean. What is the correct syntax? I am able to obtain the value from the bean as follows: <jsp:useBean id="screenBean" class="sg.com.apex.sampleapp.screenbean.DemoScreenBean" scope="session" /> <jsp:getProperty name="screenBean" property="fieldValue" />

However i am unable to get the correct way of setting this value to the custom tag's attribute. Thanks for any help...